Safety device for mechanical time fuses



April 16, 1946. J. E. MIDDLl-:Mlss 2,398,439

SAFETY DEVICE FOR MECHANICAL TIME EusEs Filed Jan. 22, 1942 figg-L JnaEPl-L E- MiddlEI-niaa @tto/Map Patented Apr. 16, 1946 UNITED; STATES PATENT orties SAFETY DEVICE FOR MECHANICAL TIME FUSES Joseph E. Middlemiss, SommertomPa. Application January 22, 19.42, Serial No. 427,723

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 1 Claim.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a safety device for a mechanical time fuse and is particularly applicable to mechanical time fuses which are adapted to be fired on shells of widely varying muzzle velocities.

In mechanical time fuses a setback pin is ordinarily provided which is displaced to the rear of the fuse on ring the projectile. This pin releases an arm on a shaft which is turned by centrifugal force causing a second arm on the same shaft to press against the timing disk. When the timing disk turns the second arm can, after the escapement has run for a predetermined time, slip into a slot and thus release a firing pin to detonate an explosive charge. An additional safety device is ordinarily provided in the form of a small arm which is free to pivot and which upon being displaced by centrifugal force unlocks the balance lever of the escapement allowing it to oscillate.

It is the primary object of the present invention to provide a new escapement lock for a mechanical fuse, which is more sensitive than those heretofore known. It is a further object of this invention to combine the action of the setback pin with the escapement lock to produce a fuse which is very safe to handle. Another object of this invention is to provide a fuse which is positive in its action so that duds are prevented, particularly in the case of fuses where all or a portion of the energy necessary to run the escapement is supplied by a spring.

The above objects are accomplished by providing a sliding release for the escapement lock and placing the release in such a position that it engages the setback pin and therefore cannot move until the setback pin is displaced by the forward movement of the projectile.

Figures 1 and 2 represent a plate of a mechanical time fuse containing the escapement release of the present invention.

Figure 3 represents a plate of a fuse containing an escapement lever. It should be noted that Figures l and 2 represent the bottom plan view of a plate, while Figure 3 represents the top plan view of a different plate.

Figure 4 is a detailed drawing of the. escapement release of this invention.

Figures 5 and 6 are cut-away drawings of three plates of a mechanical time fuse, along the lines 5-5 and 6 6 of Figures 2 and 3, respectively.

Referring now to the drawing by reference characters, there is shown in plate I a radial groove 2, one end of which communicates with a hole 3, adapted to receive a setback pin I. Groove 2 is adapted to receive a sliding release member 4, which is provided with an arm 5, which contacts the setback pin I0. It is also provided with a pin 6 which slides in a slot II of plate I2. Plate l contains an escapement lever 8 provided with a hair spring 9. The pin 6 of the release moves through the slot II cut in plate I2. When the fuse is inoperative as is shown in Figures 1 and 5, the pin 6 engages the escapement lever 8 preventing its movement, and tension on pin 5 from the escapement lever 8 and hair spring 9 also tends to prevent the movement of release 4. 'Ihe setback pin I0 prevents the rotation of arm I3 on shaft I4. Shaft I4 has another arm I 8 at its upper end which presses against the timing disk and also has a slot I9 at its lower end through which the release 20 for the firing pin 2| may slip by rotation about its pivot 22 after shaft I4 has turned. When the setback pin is displaced, as is shown in Figure 6, shaft I4 can turn suiiciently to press the upper armagainst the timing disk, but cannot turn sufficiently to detonate the fuse until the .timing disk turns a predetermined amount to allow the upper arm to slip into a slot in the disk. The release member 4 is also prevented from moving by the lower end of the setback pin I0.

When the projectile to which the fuse is attached is fired, the setback pin IIJ is forced to the rear by inertia (downward in the drawing) as is shown by Figure 6. This releases arm I3 allowing shaft I4 to turn. Shaft I4 is turned by centrifugal force acting on a small weight 23 at its upper end. This downward displacement of the setback pin IIJ also permits the free movement of the release 4 in slot 2. Centrifugal force causes release 4 to be displaced as is shown by Figures 2 and 6 which disengages pin 6 from balance lever 8, allowing it to oscillate and operate an escapement mechanism.

A further advantage of the present invention is that by combining the function of the setback pin with the balance lever release, it is possible to lock the escapement mechanism by hand operated mechanical means outside the fuse. Thus an external pin I'I may be inserted in slots I6 and I5 of plate I2 which will lock not only the setback pin (and thus the firing pin) but also the balance lever release 4 which depends on the displacement of the setback pin for its own displacement.

It will be noted that member 4 when in its outand having a. setback safety member serving toblock the firing elements of the fuse in unarmed position, the improvement comprising a centrifugally operable substantially L-shaped blocking member for the escapement lever slidably mounted for radial movement on one of the fuse body plates, the adjoining plate above the su porting plate being provided with a similarly shaped recessv for retaining, guiding, and limiting the movement of said blocking member, the supporting plate being provided with a slot, a pin carried by the blocking member extending through the slot to normally block the escapement lever, the foot of said L-shaped member being normally in the path of movement of the setback Vsafety member, the blocking member being manually operable to clear the path of the setback safety member and simultaneously block the escapement lever before the setback safety member can be positioned to restrain the blocking member.

JOSEPH E. MIDDLEMISS. 

